<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    table {
      border: 1px solid #000;
      text-align: center;
      width: 300px;
    }

    th,
    td {
      border: 1px solid #000;
    }

    h3 {
      position: relative;
    }

    span {
      position: absolute;
      left: 145px;
      top: -4px;
      width: 16px;
      height: 16px;
      color: white;
      font-size: 12px;
      text-align: center;
      border-radius: 50%;
      background-color: #e63f32;
    }
  </style>
</head>

<body>

  <div id="app">
    <!-- 使用methods 方法 没有缓存，他是直接调用方法，每次都会重新计算 -->
    <!-- <h3>小黑的礼物清单🛒<span>{{getTotal()}}</span></h3>
    <h3>小黑的礼物清单🛒<span>{{getTotal()}}</span></h3>
    <h3>小黑的礼物清单🛒<span>{{getTotal()}}</span></h3>
    <h3>小黑的礼物清单🛒<span>{{getTotal()}}</span></h3> -->


    <!-- computed 计算属性 有缓存，他只会在依赖的数据发生变化时才会重新计算，不会每次都重新计算 -->
    <h3>小黑的礼物清单🛒<span>{{total}}</span></h3>
    <h3>小黑的礼物清单🛒<span>{{total}}</span></h3>
    <h3>小黑的礼物清单🛒<span>{{total}}</span></h3>
    <h3>小黑的礼物清单🛒<span>{{total}}</span></h3>
    <table>
      <tr>
        <th>名字</th>
        <th>数量</th>
      </tr>
      <tr v-for="(item, index) in list" :key="item.id">
        <td>{{ item.name }}</td>
        <td>{{ item.num }}个</td>
      </tr>
    </table>

    <p>礼物总数：{{total}} 个</p>
  </div>
  <script src="./vue.js"></script>
  <script>
    const app = new Vue({
      el: '#app',
      data: {
        // 现有的数据
        list: [
          { id: 1, name: '篮球', num: 3 },
          { id: 2, name: '玩具', num: 2 },
          { id: 3, name: '铅笔', num: 5 },
        ]
      },
      methods: {
        getTotal() {
          console.log("这是methods方法");
          return this.list.reduce((total, item) => { return total + item.num }, 0)
        }
      },
      computed: {
        total() {
          console.log("这是computed方法");

          return this.list.reduce((total, item) => { return total + item.num }, 0)
        }
      }

    })
  </script>
</body>

</html>